Meteorological wind events, such as those caused by storms including cyclones, which cyclones may commonly be referred to as tropical storms, tropical depressions, typhoons and/or hurricanes, depending on region, size, and/or intensity are well known to generate specific wind conditions that are damaging to structures, including residential and commercial buildings. More generally, strong winds may form as a result of other types of severe weather, including storms generating gale-force or stronger winds that may also cause structural damage, depending upon specific conditions. Additionally, more localized severe wind events, such as tornadoes, may be spawned by the above conditions and events which may be expected to cause significant property damage due to wind intensity, direction, and duration over the course of the event.
Wind events may have varying degrees of predictability, depending on the conditions and circumstances that lead to their development. For example, forecasting the movement, track, size and strength of a typical tropical cyclone has improved to the point where a reliable three-to-five day warning can be issued regarding a reasonable probability of landfall in a particular area. Of course, as the storm approaches, the accuracy of the prediction improves. By contrast, events such as tornados are typically far less predictable. To the extent that hurricanes may predictably spawn tornados, the forecasting of any individual tornado remains elusive.
Wind damage to buildings is quite common after gale-force winds. Strong winds cause damage to buildings in a variety of ways, however one known phenomenon is often responsible for the shearing off of a building roof. In particular, horizontal winds resulting from storms such as a hurricane may cause aerodynamic lift on a roof, causing it to separate from the rest of the structure. Lacking the protection of a roof structure, complete destruction of the building may result. Wood-frame construction standards common in the United States are thought to be particularly susceptible to wind damage. Elevated construction requirements have been proposed for, or in place, in certain regions at high risk of storm damage, however even homes or commercial buildings built using other materials such as concrete masonry units are likely to lose their roof in a hurricane, particularly when the roof is engineered of wood.
Previous attempts to ameliorate the risk of storm event related wind damage have concentrated on holding a roof in place using belts, ropes or meshes, anchored to the ground or foundation of the underlying structure. These devices are characterized by the static force applied to hold the structure together. Static load on roof, straps, ropes and anchors are higher than needed for the protection of the roof when there is no significant wind, and may be lower than required when gusts of strong wind apply, producing among other impacts, strong uplift on the roof.
As a consequence, most of the time the load on the system is higher than necessary, while in moments of especially strong winds, protection of the building is possibly insufficient. This leads to situations where a building may be damaged by wind despite the protection measures, or instead where the roof may be subject to long periods of overstress.